Recently, the market has demanded more that new values, such as option expandability and energy saving, be added to image forming apparatuses. In addition, it has been required to supply power from an image forming apparatus to an optional apparatus so as to improve the design of the optional apparatus when it is mounted and allow a user to easily detach/attach it.
When, however, power is to be supplied from the image forming apparatus body to, for example, an optional apparatus designed to perform stapling processing, since high power is required for stapling operation, a large-capacity power supply circuit must be prepared for the image forming apparatus body in expectation of the maximum load on the optional apparatus. This leads to an unnecessary increase in cost for a user who uses only the image forming apparatus. It has therefore been required to minimize an increase in the cost of the image forming apparatus body by reducing the maximum power consumed by the optional apparatus itself.
In addition, a demand has arisen for a means for reducing the maximum powers of an image forming apparatus and optional apparatus to prevent the maximum power of the system from exceeding the maximum power that can be supplied from a one-system commercial power supply so as to prevent a protective means such as the circuit breaker of the commercial power supply from activation.
On the other hand, an image forming apparatus or an optional apparatus individually having a power supply uses an arrangement designed to cut off, for safety, power supplied to a driving means, heating means, or the like placed at a position where a user can touch when the user opens the image forming apparatus in case of paper jam.
When a storage battery is provided for an optional apparatus which receives power from an image forming apparatus, the following problem arises. Although power from the image forming apparatus to the optional apparatus is cut off when the optional apparatus is detached from the image forming apparatus or the optional apparatus is opened, electric charge remaining in the storage battery may allow a driving means of the optional apparatus to operate.